Biological oxidation processes of macromolecules play important roles in aging and in the pathogenesis of common diseases, including heart and lung pathologies. While the detailed mechanism of protein oxidation is not completely understood, it has been proposed that it requires the involvement of catalytic levels of redox active iron (or copper). Earlier studies on protein and amino acid oxidation have already shown that a unique "blue" complex is formed among iron, ferrozine (a potent iron chelator), and an amino acid. Among the amino acids, histidine, frequently found in active sites, makes an especially stable complex. We demonstrated that the blue species readily oxidizes in air and that the ferrous iron oxidizes to the ferric state. Also, the blue complex contains iron ion, two ferrozine molecules, and an amino acid molecule. We also showed that iron recycles between its oxidation states, dissipating ascorbate (or hydroxylamine). The blue species could constitute a pathway and a model for protein oxidation. Polychlorinated phenols are biocides, ubiquitously used in agriculture and industry, and have been incriminated as teratogenic and carcinogenic in man and animals. The mechanism of their action is not fully understood. It has already been shown that iron is an essential component for the manifestation of their toxicity, and that free radicals are involved in the injurious process(es). While early gene activation (SoxS or OxyS) does seem not important in the cellular (E. coli K-12) response to pentachloropenol, protein oxidation was the only identified molecular pathway of cellular damage.